Cutting rule and perforated line



0a. 18, 1960 c. D. MINGQ 2,956,465

. CUTTING RULE AND PERFORMED LINE Filed May 19, 1955 it hi M ATTORNEY United States Patent CUTTING RULE AND 'PERFORATED 'IJINE Cyran D. Mingo, Minneapolis,.Minn assigilor to Wal dorf Paper Products company,.st. Paul, Minn, a corporation of Minnesota Filed May 19, 1955, Ser. No. 509,636-

lClaim. (Cl. 83-660) This invention relates to an improvement in method and apparatus for forming a perforated hne as long-as the structure of the finished'productL The use of perforated lines in folded cartons andthe like is extremely oldin the art. It' is common practice to perforate the carton stock along desired lines with a cutting rule having spaced' teeth therein to provide a weakened line along which the carton may be cut or torn. One of the difliculties involved in such an arrangement lies in the fact that the carton stock is usually extremely weak along the line of perforations. For example, if a perforated line is provided extending about the walls of a carton at points spaced from the end closures, the carton stock is likely to kink inwardly at the point of the perforated line so as to expose the container prematurely. Any force or blow against a panel contain ing a perforated line has a tendency to cause the panel to fold along the line of perforations. This is very undesirable where the carton must possess some degree of strength or rigidity.

An effort is usually made to balance the strength requirements against the necessity for easily opening the container. For example, by varying the length and frequency of the teeth and varying the space between the teeth, the resistance to folding along the perforated line may also be varied. However, as the distance between the teeth increases, the difficulty of tearing the carton along the perforated line also increases. It is extremely ditficult to produce a perforated line which will resist folding and which at the same time will be simple and easy to tear. An object of the present invention resides in the provision of a perforated line which is easy to tear and yet which resists folding along the line of perforations. Such a line of perforations is produced by the use of a corrugated section of cutting rule provided with spaced notches normally at the peaks of the corrugations. This type of cutting rule forms cut lines or slits in the paperboard which are alternately angled, one slit inclined upwardly and the next slit inclining downwardly or at the opposite angle. The ends of these inclined slits are spaced apart and the board may be torn along the corrugated line, the line of tear being wavy or generally similar to the shape of the corrugated cutting rule. At the same time a structure is provided which is resistant to bending due to the fact that the lines along which the carton board is torn are off set one from another.

A feature of the present invention lies in the provision of a weakened line of separation which includes alternately angled slits arranged in spaced relation, one pair of slits having their upper ends inclined toward each other and terminating in spaced relation and the alternate ends of the slits inclining downwardly toward one another, terminating in spaced relation along a line parallel to and spaced from a line through the upper ends of the slits. In tearing open the paperboard along such a perforated line, the paper tears first along a line through the upper ends of the slits and next along through the lower ends of the slits forming a wavy outline. With such an arrange- "ice ment the paperboard is resistant to bending along either of the lines of tear.

Theseand other objects and novel features of my invention will be more clearly and fully'set forth in the following. specification and claim.

In'=the"drawings forming apart ofthe specication:

Figure 1 is a perspective view ofa' carton havinga perforated line extending around the same at a point spacedf'rom an end thereof.

Figure'i2 is a section of the blank forming the carton shown in Figure 1 showing the arrangement of slits forming the perforated line.

Figure'3'is a perspectiveview of a small section of the perforating rule used to form the perforated line shown in Figures'l and 2.

Figure 4'is a view looking toward the cutting edge of the perforating rule.

Figure Sis an elevational view of the cutting rule of the type shown in Figures 3 and 4.

The carton is indicated in general by the leter A and may be of any type or shape. Actually the perforated line made in accordance with my invention may be used in any piece of paperboard or similar material but is shown as embodied in a carton as such perforated lines are commonly used in such locations. The carton A is a. regular rectangular tubular carton having side walls such as 10 and end walls such as 11 and end closures such as 12 which are usually formed by-folding closing flaps into superimposed relation.

The perforated line is indicated generally by the numeral 13 and extends around three or four walls of the carton in common construction so that the top portion of the carton may either be removed or may be hinged into open position.

-As indicated in Figure 2 of the drawings, the carton walls 16 and 11 are perforated along a line parallel to the fold line 14 connecting the carton side and end walls to the closing flaps such as 15 and 16. The perforated line 13 includes alternate parallel slits 17 which inclinein the same direction and extend diagrammatically of the panel in which they are formed. The perforated line ineludes alternate cut lines 19 which are parallel and which incline in a direction opposite the direction of inclination of the lines 17. As a result, the upper ends of two adjoining cut lines or slits are spaced apart a predetermined distance while the upper ends of each of these slits is spaced at relatively long distance from the upper end of the next adjacent slit. Similarly the lower ends of alternate pairs of slits are relatively close together while the lower ends of these same slits are substantially farther from the lower ends of adjoining slits.

As the carton stock or other material will naturally tear along the line of least resistance, the stock will tear between the adjacent ends of the slits, but will not tear between the ends of the slits which are farthest apart. As a result, the carton stock will tear along a line through the upper ends of the slits between two adjoining slits and will then tear along a line through the lower ends of the slits where the lower ends are close together. As a result, the edges of the paperboard will be wavy or undulated when the carton stock has been torn.

In order to produce the perforated line in a simple and effective manner, corrugated cutting rule is employed. Such rule is usually formed by passing the straight flat cutting rule between suitable gear-like rollers which bend the rule first in one direction and then in the other. This corrugated rule is readily available where cutting rule may be sold.

The corrugated cutting rule is then notched preferably at the apexes of the corrugations. The notching means used may be similar to that used for producing corrugated rule of conventional form or may be formed by 3 special uotching means. gations are notched, the remaining cutting edge comprises sharpened portions alternately inclining in opposite directions. Such a corrugated rule is indicated at 20 and the notches. in the cutting edge are indicated by the numeral 21.

In view of the fact that the corrugated rule is usually provided with corrugations which are not of great depth and in view of the further fact that corrugating the rule acts to strengthen it, the corrugated rule may be placed between blocks which engage only the apexes of the corrugations. In other words it is not necessary to jig-saw the wood forming the die along a corrugated path as the corrugated rule will maintain its proper relation without such support.

A panel of paperboard bearing a perforated line of usual construction will fold readily with but little pressure along the line of corrugations. Much greater pressure can be applied on opposite sides of a panel having a corrugated line of the type disclosed without creating any marked fold. Obviously the paperboard must fold along a line through the upper ends of the slits, through the lower ends of the slits, or along two lines through both ends of the slits. This requires the folding of portions of paperboard which are quite lengthy due to the fact that the distance between alternate pairs of slits is relatively long.

In accordance with the patent statutes, I have described the principles of construction and operation of my method of forming a perforated line, and while I have endeavored to set forth the best embodiment thereof, I desire to have it understood that obvious changes may be made within When the apexes of the corruthe scope of the following claim without departing from the spirit of my invention.

I claim:

A cutting rule for forming a wavy perforated line in a body of paperboard, the cutting rule comprising a strip of constant width having substantially V-shaped corrugations therein extending transversely to the longitudinal axis of the rule, one end of said corrugations lying in a single plane and beveled to form a corrugated cutting edge on said cutting rule, the cutting edge of the cutting rule having notches therein at the apexes of each of the corrugations, said notches having straight side walls parallel to said corrugations and longer than the thickness of said paperboard.

References Cited in the file of this patent UNITED STATES PATENTS 676,781 Stimpson June 18, 1901 909,145 Brunson Ian. 12, 1909 1,453,200 Stacho Apr. 24, 1923 2,266,958 Corbin Dec. 23, 1941 2,363,861 Goodyear Nov. 28, 1944 2,432,176 Schubring Dec. 9, 1947 2,519,552 Eller Aug. 22, 1950 2,522,440 F-reter Sept. 12, 1950 2,680,558 Mai June 8, 1954 FOREIGN PATENTS 491,424 France June 3, 1919 668,970 Germany Mar. 17, 1939 663,958 Great Britain I an. 2, 1952 695,331 Great Britain Aug. 5, 1953 

